1. Field of the Invention
The present invention relates to a neighbor cell notifying apparatus and a neighbor cell notifying method for notifying a mobile station of predetermined information in a mobile communication network for implementing wireless communication utilizing a plurality of cells between the mobile station and a base station.
2. Related Background Art
The W-CDMA (Wideband-Code Division Multiple Access) system, or the UMTS (Universal Mobile Telecommunications System) in IMT-2000 (International Mobile Telecommunications-2000) being a typical mobile communication system adopts DHO (Diversity HandOver) to implement communication simultaneously using a plurality of cells and effect combination and selection of signals, thereby improving the quality. In the W-CDMA system, or the UMTS, information about neighbor cells for a mobile station under communication to monitor in preparation for handover is retained as system data or the like at a radio control station, and the mobile station under communication is notified of the information by a message. Neighbor cell information items corresponding to the respective cells are transmitted to the mobile station under communication using the plurality of cells in DHO.
There is sometimes a limit to the total number of neighbor cells that can be notified of and monitored, from performance restrictions at the mobile station. Therefore, in the case of the communication using a plurality of cells in DHO, there is a technique of extracting duplicate cells among the neighbor cell information items of the cells and avoiding transmission of the neighbor cell information items about the duplicate cells, in order to increase information efficiency of the neighbor cell information transmitted from the radio control station to the mobile station.